The present invention generally relates to a paper sheet feeding apparatus and more particularly to an apparatus for serially feeding flat sheets of paper from the bottom of a vertical stack of such sheets and so as to permit subsequent processing of each individual sheet.
Generally, sheet feeding machines capable of high speed feeding are relatively complicated, and require a large number of complex and interrelated moving parts which are subject to wearing out and failure.
U.S. Pat. No. 4,991,831 discloses an improved sheet feeding apparatus wherein a gate forming member is positioned above the upper run of a belt feeding system so as to define a nip therebetween. The gate forming member mounts a plurality of elastomeric rings in eccentric grooves, so that the rings are not exposed on the side of the roll facing the stack of sheets being fed, but the rings are exposed at the nip. The nip is sized for permitting the lowermost sheet of the stack to pass freely through the nip, while the sheet immediately above the lowermost sheet is retarded by its frictional engagement with exposed portions of the rings.
While the sheet feeding apparatus as disclosed in the '831 patent represents a significant advance in the art and has enjoyed commercial success, the manufacturing cost associated with the formation of eccentric grooves in the roll is relatively high. Also, the mechanism for adjusting the nip opening size to accommodate paper sheets of varying thickness requires manual adjustment in all cases, and is not susceptible to an automatic operation.
It is accordingly an object of the present invention to provide a sheet feeding apparatus of the described type having a reduced manufacturing cost, and which is able to permit almost automatic adjustment of the nip opening size to accommodate sheets of paper of different size and weight.